The field of invention relates generally to optical communication systems; and in particular but not exclusively, relates to holographic optical elements for use in optical communication systems.
With increasing popularity of wide area networks such as the Internet and/or World Wide Web, network growth and traffic have experienced tremendous growth. Network users continue to desire faster networks, which may be difficult to achieve using existing wired technologies.
An alternative to wired network solutions is a wireless or free space optical (FSO) communication technology. Such FSO systems can use beams of light, such as laser beams, as optical communication signals, and therefore do not require cables or fibers connected between transmitters and receivers.
FSO units (i.e., FSO transmitters, receivers, and transceivers) used in FSO communication systems typically include several separate optical elements for transmission, reception, tracking and acquisition of FSO signals. For example, some FSO units have multiple apertures, each having a lens. Other FSO units may have a single aperture with a lens and multiple beam splitters. Because these optical elements are relatively expensive, the cost of such a unit increases as more optical elements are incorporated into the unit. Further, these optical elements typically require relatively complex mechanisms to provide needed optical isolation between elements, which further increases costs (including design costs). In addition, as more optical elements are used in a unit, alignment and maintenance of the unit becomes more complex, thereby increasing costs and the xe2x80x9cdowntimexe2x80x9d in maintaining the unit Such increased costs and downtime are undesirable in many applications.
In accordance with aspects of the present invention, a holographic element (HOE) with multiple apertures formed in a single substrate is provided for use in an optical communication system. In one aspect, the multi-aperture HOE can be used instead of a conventional optics unit having one or more separate optical elements for each aperture. For example, the multi-aperture HOE can include a reception aperture and a tracking aperture for use in an optical receiver unit or transceiver unit. Because a single substrate is used to implement the apertures, multiple apertures can be provided for the optical unit with reduced complexity and cost relative to conventional systems that use separate optical elements to implement the optics unit.
In another aspect, the multi-aperture HOE includes a transmission aperture. In one embodiment, the transmission aperture is implemented with multiple component apertures. Multiple component transmission apertures can reduce scintillation of the transmitted optical signal. This aspect provides a relatively simple and inexpensive mechanism to reduce scintillation.
In yet another aspect, the multi-aperture HOE includes transmission and reception apertures for use in an optical transceiver.